Zinc oxide semiconductor material

ABSTRACT

A zinc oxide semiconductor material comprising at least zinc and oxygen as constituent elements, which can be deterred with respect to the deterioration of doping characteristic, luminous characteristic and the like, compared with a conventional c-axial oriented one by orienting the crystal orientation plane to a-axis of the wurtzite structure.

FIELD OF THE INVENTION

This invention relates to improvements in a zinc oxide semiconductormaterial comprising at least zinc and oxygen as constituent elements,applied for light emitting in the region of blue and near ultraviolet.

BACKGROUND OF THE INVENTION

Zinc oxide semiconductor materials comprising zinc and oxygen asconstituent elements have recently attracted considerable attentionsince they can emit not only blue light but also near ultraviolet raysof 400 nanometers or less because of their wide band gap similarly tosemiconductor materials such as gallium nitride and the like. Further,their applications to photodetector, piezoelectric device, transparentconductive electrode, active device and the like have also been expectedwithout being limited to light emitting device.

To form such zinc oxide semiconductor materials, various methods such asMBE method using ultra-high vacuum, sputtering, vacuum evaporation,sol-gel process, MO-CVD method, and the like have been conventionallyexamined. With respect to the light emitting device, the MBE methodusing ultra-high vacuum is widely used from the viewpoint ofcrystallinity. In each of these conventional growth methods, forexample, a growth method shown in Appl. Phys. Lett., 41 (1982) 958 byMinami et al., a method using a single-crystalline sapphire substratereported in Solid-State Physics, vol. 33, No. 1 (1998) by Kawasaki etal., the obtained thin film had c-axial orientation because the energyin crystal growth is the lowest in the c-axial development of thewurtzite structure.

However, not only such a crystal having c-axial orientation is apt toform a polycrystal containing nanocrystals, when the shape is evenslightly deformed in the growing stage of crystal, by minimizing thehexagonal shape to arrest the deformation, which makes it difficult toobtain a single crystal film of relatively large area, but also apolycrystal film containing the nanocrystals is apt to cause abnormalproperties in electric conduction by the bonding of impurities to theterminal of the nanocrystals or the bonding of a conductive electron toa dangling bond at the top surface, resulting in the deterioration ofdoping characteristic, luminous light characteristic, and the like.

Accordingly, this invention has been attained from the viewpoint of theabove-mentioned problems, and has an object to provide a zinc oxidesemiconductor material deterred with respect to the deterioration ofdoping characteristic, luminous characteristic and the like.

DISCLOSURE OF THE INVENTION

To solve the above problems, a zinc oxide semiconductor material of thisinvention comprises at least zinc and oxygen as constituent elements,characterized in that the crystal orientation face thereof is orientedto the a-axis of the wurtzite structure.

Whereas a c-axial orientation plane having a hexagonal crystal plane isapt to form nanocrystals by minimizing the hexagonal shape when theshape is even slightly deformed, the a-axial crystal orientation planeoriented to the a-axis of the wurtzite structure hardly forms thenanocrystals as described above because it has a rectangular shapecapable of moderating a slight strain, so that stable crystals of highquality similar to single crystal can be provided in a wide area, andthe deterioration of doping characteristic, luminous characteristic andthe like can be consequently prevented. The a-axial plane is also moreexcellent in doping characteristic than the c-axial plane, allowing thestable preparation of a semiconductor.

The zinc oxide semiconductor material of this invention preferablycontains the constituent element of a substrate material in the range of0.001–1 at. % in the interface with the substrate material where thezinc oxide semiconductor material is formed.

The lattice misfit of ZnO films with the substrate material and stressby mechanical deflection in the interface with the substrate can bemoderated by including the constituent element of the substrate in therange of 0.001–1 at. %.

The zinc oxide semiconductor material of this invention is preferablyformed by use of an organic metal of β-diketone compound as rawmaterial.

According to this, the MO-CVD method in which an inexpensive device wasusable but it was difficult to obtain a crystal of high quality can beused to prepare a zinc oxide semiconductor material at a low cost.

In the zinc oxide semiconductor material of this invention, the organicmetal of β-diketone compound is preferably zinc acetylacetonate(Zn(acac)₂; wherein ac represents acetylacetone).

By using the zinc acetylacetonate (Zn(acac)₂), not only the carbonquantity in the resulting zinc oxide semiconductor material can beminimized, but also the raw material is easily and inexpensivelyavailable because the zinc acetylacetonate is industrially produced inlarge quantities.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing the structure of a MO-CVD system to which amethod for preparing zinc oxide semiconductor material of this inventionis applied.

FIG. 2 is a model view showing the crystal structure of a zinc oxidelayer.

FIG. 3 is a view showing the molecular structure of a zincacetylacetonate monohydrate that is a zinc-containing organic compoundused in this invention.

FIG. 4 is a graph showing the differential thermal analytic (DTA) andthermogravimetric (TG) measurement results of zinc acetylacetontae andits monohydrate thereof which are zinc-containing organic compounds usedin this invention.

FIG. 5 is a view showing an applied form example of a zinc oxide layeraccording to the method for preparing zinc oxide semiconductor materialof this invention to a luminescence device.

FIG. 6 is a view showing an applied form example of a zinc oxide layeraccording to the method for preparing zinc oxide semiconductor materialof this invention to a EL device driven by DC mode.

FIG. 7 is a view showing an applied form example of a zinc oxide layeraccording to the method for preparing zinc oxide semiconductor materialof this invention to an luminescence device driven by AC mode.

FIG. 8 is a view showing an applied form example of an LED device havinga pn junction formed only by a ZnO layer according to the method forpreparing zinc oxide semiconductor material of this invention.

FIG. 9 is a view showing an applied form example of an LED device usinga ZnO layer obtained according to the method for preparing zinc oxidesemiconductor material of this invention and CuAlO₂ or NiO naturallyhaving p-type conduction.

FIG. 10 is a view showing an application example of a ZnO layeraccording to the method for preparing zinc oxide semiconductor materialof this invention to an optical pumping type laser device.

FIG. 11 is a view showing an application example of ZnO layer accordingto the method for preparing zinc oxide semiconductor material of thisinvention to a semiconductor laser device.

FIG. 12 is a view showing the reflection electron beam diffractionphotograph of a ZnO layer according to the method for preparing zincoxide semiconductor material of this invention.

FIG. 13 is a view showing the surface image by an atomic forcemicroscope (AFM) of a ZnO layer according to the method for preparingzinc oxide semiconductor material of this invention.

FIG. 14 is a graph showing the wavelength characteristic of the emissionspectrum by external excitation of electron beam irradiation of a ZnOlayer according to the method for preparing zinc oxide semiconductormaterial of this invention.

FIG. 15 is a graph showing the emission spectrum by external excitationof electron beam irradiation of a ZnO layer according to a conventionalmethod for preparing zinc oxide semiconductor material.

PREFERRED EMBODIMENT OF THE INVENTION

One preferred embodiment of this invention is further described on thebasis of the accompanying drawings.

A metal-organic chemical vapor deposition (MO-CVD) apparatus forpreparing a ZnO layer that is a zinc semiconductor material according tothis invention is shown in FIG. 1. In this invention, since theatmospheric pressure MO-CVD method is easily transferable to industrialmass production due to the avoidance of the need for ultra-high vacuumas in the above MBE method but also the execution of the vapor phasedevelopment at atmospheric pressure is applied, no large-sized vacuumequipment for evacuating a reaction chamber 1 that is a chamber forperforming chemical vapor deposition (CVD) is connected to the reactionchamber 1, and an exhausting fan 7 for properly exhausting the gas inthe reaction chamber 1 to the outside is mounted on the upper positionof the reaction chamber 1.

A glass cylinder 13 filled with powdery zinc acetylacetonate (Zn(acac)₂)monohydrate that is the source material of ZnO layer is connected to thereaction chamber 1 through a source material inlet tube 22, and the zincacetylacetonate (Zn(acac)₂) monohydrate heated and sublimated by asublimation heater 14 arranged so as to be heatable of the sourcematerial cylinder 13 is supplied through the lower side of the reactionchamber 1 for growing the layer by the nitrogen (N₂) carrier gas run outfrom a nitrogen tank 16 connected to the source material cylinder 13through a nitrogen inlet tube 17 and controlled in flow rate by anitrogen flowmeter 15 and a flow variable valve VL1. The temperature ofthe source material cylinder 13 is controlled to a preset prescribedtemperature by a sublimation temperature controller.

An oxygen tank 19 that is the supplying source of oxygen for the ZnOlayer to be formed is connected to the reaction chamber 1 through anoxygen inlet tube 20 separately provided from the raw material inlettube 22 in order to avoid the gas phase reaction of oxygen gas (O₂) withthe zinc acetylacetonate (Zn(acac)₂) monohydrate, and an oxygenflowmeter 18 and a flow variable valve VL2 are provided in the inflowroute of the oxygen, so that the oxygen (O₂) gas controlled in flow rateis supplied through a preheating promoting porous metal plate 10provided adjacently to a substrate 3 in the reaction chamber 1, and theoxygen (O₂) gas is supplied separately from the zinc acetylacetonate ofsource material up to just the front of the substrate.

A preheating heater 9 is provided on the circumference of the lowerspace 2 of the reaction chamber 1 for discharging the zincacetylacetonate monohydrate supplied into the reaction chamber 1together with the nitrogen (N₂) carrier gas to preheat the vapor of zincacetylacetonate monohydrate introduced into the reaction chamber 1 inthe lower space 2 before it reaches the substrate 3 on a substrateholder 4 provided in the upper position within the reaction chamber 1.The preheating temperature is controlled to a prescribed temperature bya preheating temperature controller 11 connected to the preheatingheater 9.

On the reverse (upper) side of the substrate holder 4 provided in theupper position within the reaction chamber 1, a substrate heating heater5 for heating the substrate 3 is provided on a sample holder 6 (on thelower surface) to control the temperature of the substrate 3 heated bythe substrate heating heater 5 to a prescribed temperature by asubstrate temperature controller 8.

The zinc acetylacetonate monohydrate used as the source material in thisinvention is a white powder at room temperature, and the powder isfilled in source cylinder 13. However, this invention is never limitedthereby, and the zinc acetylacetonate monohydrate may be pelletized in aprescribed size and filled in the cylinder 13 from the point ofimprovement in handling property when mass productivity is taken intoconsideration. The heating of the filled zinc acetylacetonatemonohydrate may be carried out by introducing the nitrogen (N₂) carriergas heated to a prescribed temperature into the cylinder 13 to obtainsublimated zinc acetylacetonate vapor.

The zinc acetylacetonate monohydrate which is the supplying source ofzinc has a structure as shown in FIG. 3, wherein a water molecule iscoordinate-bonded to zinc atom with oxygen as a ligand. As the zincacetylacetonate, those with purity of 99.8–99.99% are generallycommercially available as reagents, wherein a hydrate and a non-hydrateare included. However, when such a reagent including the hydrate andnon-hydrate is used as source as it is, the reproducibility ofcrystallinity is inferior in the non-hydrate, and the hydrate exhibitsmore satisfactory reproducibility. Accordingly, the simple substance ofa hydrate is preferred for a stable production.

The cause of this difference in reproducibility is attributable to thatthe oxygen atom of the water molecule is coordinate-bonded to the zincatom itself in the hydrate, and the oxygen atom in the water molecule isused as the oxygen atom used for a part of the generation of the ZnOlayer in addition to the oxygen in air to provide the stablereproducibility of crystal growth. The zinc acetylacetonate includesseveral kinds of hydrates with a plural coordination of water moleculescoordinated thereto, and the monohydrate is preferable among them fromthe point of stability of hydrate in addition to the ratio of oxygenatom in water molecule to zinc atom. However, this invention is neverlimited by this.

The use of zinc acetylacetonate as the zinc-containing organic compoundas in this embodiment is preferable because the zinc acetylacetonateitself is industrially mass produced and inexpensively and easilyavailable as described later. However, this invention is never limitedthereby and, for example, zinc dipivaloylmethanate (DPM) and otherzinc-containing organic compounds which exhibit relatively lowreactivity with oxygen may be used as the zinc-containing organiccompound.

Needless to say, it is optional to add a specified quantity of anacetylacetone metal or dipivaloylmethanate (DPM) metal such as Li and Cuof the group I compounds, B, Ga, In, Al or the like of the group IIIcompounds, and the like as the supplying source of a doping element forforming P-type and N-type of semiconductor.

Whereas diethyl zinc used in conventional metal-organic chemical vapordeposition (MO-CVD) is explosively reacted with the oxygen in air andburnt at room temperature, this zinc acetylacetonate as the supplyingsource of zinc is relatively stable from room temperature to a regiontemperature for plastic synthesis as is apparent, for example, from thatit is industrially used in large quantities as a plastic stabilizerbecause of the property of zinc of absorbing chlorine radicals generatedin the plastic synthesis of vinyl chloride or the like, and thereactivity with oxygen is remarkably low, compared with the diethylzinc. This can be understood from the differential thermal analytic(DTA) and thermogravimetric (TG) measurement results of zincacetylacetone and zinc acetylacetonate monohydrate shown in FIG. 4, andalso from the remarkably smaller quantity of carbon atom left in theresulting crystal in the zinc acetylacetonate. The differential thermalanalysis comprises measuring an endothermic or exothermic reaction inthe change of the structure of a material. The thermogravimetrycomprises measuring the weight change in the sublimation or evaporationof the material. The weight change shows a different value inconformation to heating speed, but the endothermic or exothermicreaction shows a value natural to the material. The measurementcondition for DTA and TG is set to an atmospheric environment with atemperature rise speed of 10° C./min and N₂ gas flow rate of 200 cc/mm.

In the TG curve of the monohydrate in FIG. 4( a), the weight starts todecrease little by little from at about 50° C., and a large endothermicreaction is observed in the DTA curve. This is attributable to that thewater molecule coordinate-bonded to the zinc atom of the zincacetylacetonate monohydrate absorbs the vaporization heat forevaporation according to temperature rise, and its vaporization quantityis gradually increased. When the material is further heated, the weightreduction sharply increases from at about the melting peak (132.1° C.)of the DTA curve. The TG curve in FIG. 4( b) of the zinc acetylacetonatethat is a non-hydrate uniformly decreases from at about 60° C., andsharply decreases from at about the melting peak (133.4° C.) slightlyhigher than that of the hydrate. The melting point is also important forthe formation of a ZnO thin film of good quality, and preferably set tothe range of 132° C. to 135° C.

The zinc acetylacetonate and zinc acetylacetonate monohydrate arerelatively low in reactivity with oxygen gas, and require the use ofpure water as the supplying source of oxygen. However, it is known thatthe water condensed in the low-temperature area of a pipe or device isre-evaporated according to the ambient temperature rise in the use ofpure water as raw material in the atmospheric pressure CVD process,making it difficult to obtain the reproducibility of layer composition.This is very likely to obstruct the industrial production process.Therefore, in the above device, the zinc acetylacetonate is preheated inthe lower space 2 of the reaction chamber 1 as described above for thepurpose of compensating the low reactivity of the zinc acetylacetonatewith oxygen gas, whereby the reactivity with oxygen on the substrate 3is promoted.

The preheating promoting porous metal plate effectively functions todecompose the zinc acetylacetonate that is an organic metal. The zincacetylacetone is carried by N₂ carrier gas of about 200–1000 cc/min.Although the glass tube wall is warmed by use of a heater wound aroundthe preheating area, the staying time of the zinc acetylacetonatematerial in the preheating area is shortened by the relatively high flowvelocity of the carrier gas, and the heating of the material sufficientfor promotion of decomposition cannot be performed. The preheatingpromoting porous metal plate has a double effect of the increase instaying time and the promotion of decomposition by the direct contact ofthe zinc acetylacetonate to the preheating promoting porous metal plate.The decomposition of the zinc acetylacetonate can be controlled by theseeffects.

The preheating promoting porous metal plate is manufactured by boringholes of about 0.1–5 mm in a metal plate of stainless steel or the like.To reduce the temperature drop of the substrate surface by thehigh-speed carrier gas blown out from the holes of the metal plate, alarge number of metal plates may be stacked while shifting the positionsof holes and providing a clearance.

The edge of the metal plate is desirably in contact with the glass tubewall of the reaction chamber to prevent the zinc acetylacetonatematerial not promoted in decomposition from flowing out through theclearance between the reaction chamber and the metal plate.

The material for the metal plate is required to be a metallic materialresistant to a temperature of 200° C. or higher. The use of the metalplate is general, but a material such as ceramic, mesh, glass wool orthe like may be substituted therefor.

In the formation of the zinc oxide layer, the temperature of thepreheating promoting porous metal plate is preferably set to the rangefrom the sublimation temperature of zinc acetylacetonate to thevaporization temperature thereof. The temperature range is desirablywithin 100–400° C., more preferably 125–250° C.

In the ZnO layer formed on the substrate 3 in the above device by use ofthe acetylacetone zinc monohydrate, as shown in FIG. 2 (002) planeoriented to c-axis of the wurtzite structure and (110) plane and (100)plane oriented to a-axis thereof are used as the crystal orientationplane in the use as light emitting device. Whereas the c-axial plane isapt to cause an abnormality in crystal growth because of the hexagonalcrystal orientation, so that the crystal size is apt to be fined togenerate nanocrystals, the a-axial planes (110) and (100) hardly causethe abnormal growth because of the tetragonal crystal plane and theinclusion of Zn atoms and O atoms on the crystal plane, so that acrystal of high quality can be obtained.

In this embodiment, a single crystal sapphire substrate that is aheteroepitaxial substrate is used as the substrate 3. The sapphiresubstrate has a corundum structure, and a c-plane substrate having (002)plane and a R-plane substrate obtained by obliquely cutting the crystalplane are prepared. The R-plane substrate is not only mass produced as asubstrate (SOS substrate) for a silicon epitaxial growth layer, but alsohas the merit that a relatively large substrate is easily availablebecause the crystal is obliquely cut, and it is suitable for thesubstrate 3. In this invention, the ZnO layer having (110) orientationis grown on the R-plane substrate free from abnormal growth. Further,this layer is excellent in crystallinity and satisfactory in dopingcharacteristic, compared with a sample with (002) c-axial orientation.

The substrate 3 to be heteroepitaxially grown is not limited by thesapphire substrate, but includes other substrates such as Si, SiC, Ge,Ga, GaN, GaAs, ZnS, ZnSe, diamond, MgO, MgAlO₃, ZrO₂, CuAlO₃, ZnMgO₃,and the like. However, the lattice constant value of the substratematerial is required to be within 20% of the lattice constant of the ZnOlayer. When the lattice constant difference exceeds this, a defect byabnormal growth occurs in the developed ZnO layer. When the lightemitting device to be formed requires the multifunctionalization of adrive circuit or the like, a lattice mismatch exceeding 20% might occur.In this case, an intermediate layer may be provided to adjust thelattice mismatch to 20% or less in the interface with the ZnO layer.

When the substrate material is a different kind material such assapphire substrate or the like as described above, in addition to thelattice mismatch, a mechanical stress is necessarily generated in theinterface between the substrate material and the ZnO layer as lightemitting device. Accordingly, the instantaneous switching of compositionin the interface between the substrate material and the ZnO layer is notpreferred because chemical and mechanical stresses are increased. Thus,the constituent element of the substrate material is preferably diffusedto the ZnO layer side in the interface between the ZnO layer that is alight emitting material and the substrate material, and the quantity ofdiffusion is preferably set so that at least one of the constituentelements of the substrate material is included in the range of 0.001–1at. % from the initial growth stage of the light emitting device to theposition of 50A. When the element is included more than this, theconstituent element of the substrate material seriously affects asimpurities in the ZnO layer to disturb the growth of the single crystallayer. The addition quantity thereof is adjusted, for example, bychanging the substrate temperature in the initial growth stage, addingonly a trace amount of the constituent element of the substrate asimpurities in the initial growth stage of the ZnO layer, or the like.

The thus-formed ZnO layer is usable as light emitting device, forexample, in a luminescence device, LED device, laser device or the like.

The luminescence devices using ZnO layer include an element performingan external excitation with an external light source such as laser,electron beam or the like and an EL device performing an internalexcitation driven by DC or AC mode. The structure of the deviceperforming external excitation by laser or electron beam or the like isshown in FIG. 5. A band edge emission is caused in ultraviolet region bythe external excitation. FIG. 6 shows an example of a DC EL device. Inthe DC device, an electrode is used as a Schottky junction. As thematerial of the Schottky electrode, Au, Pt, Pb and the like having alarge work function is used. In the AC exchange impression device, asshown in FIG. 7, an insulating material is put between ZnO and anelectrode. Examples of the insulating material include SiO₂, Si₃N₄, MgO,and MgAlO₃.

The LED devices include a one having a pn-junction formed only by ZnO asshown in FIG. 8, and a one comprising CuAlO₂ or NiO naturally havingp-type conduction formed in the p-type layer as shown in FIG. 9.

The laser devices include an external excitation type shown in FIG. 10and a semiconductor laser device. The structure of external excitationdevice has a reflector formed on a luminescence device. The dielectricmirror which accumulates a metallic material and dielectric substancessuch as Al and Au is used as a stuff of the reflection mirror. Thesemiconductor laser preferably forms a double hetero structure as shownin FIG. 11 from the point of emission efficiency. The cladding layer ofthe double hetero structure includes CuAl₂, MgZnO₃ and the like whichhave a wider band gap than ZnO. As the material for the reflector, thesame ones as used for the external excitation laser are applicable.

Photodetector is finally integrated to the substrate having the lightemitting device formed thereon, and the output of this photodetector isfed back to control the input current of the light emitting element,whereby the output of the light emitting device can be limited. For thisphotodetector, a ZnO layer formed of the same material as the lightemitting device can be used. An optical modulator for controlling thelight output of the light emitting device can be also formed on the samesubstrate. Since the ZnO layer functions as a piezoelectric device, asurface acoustic wave (SAW) device can be formed. This device is locatedon the output side of the light emitting device, whereby the emissionoutput can be modulated, or the emission output can be stabilized.Further, it is formed in a resonator within the reflector, whereby aQ-switch type pulse laser can be also formed.

EXAMPLE

This example is an application example of a ZnO layer to an externalexcitation luminescence device. For the substrate 3 for forming the ZnOlayer, a single crystal sapphire R-plane was used. Zinc acetylacetonate[Zn(C₅H₇O₂)₂] of purity 99.99% was used as a zinc source organiccompound, and O₂ gas of purity 99.99% was used as an oxygen source. TheZnO layer growth condition was set to a substrate temperature of 475°C., an oxygen flow rate of 400 cc/min, and a nitrogen flow rate ascarrier gas of 200 cc/min. The sublimation and preheating were carriedout at 124° C. as the set temperature of the sublimation temperaturecontroller 12 and at 160° C. as the set temperature of the preheatingtemperature controller 11, respectively. The temperatures of thesublimation and preheating may be properly selected on the basis of thekind or reactivity of the zinc-containing organic compound to be used.

The structural evaluation and surface observation of the ZnO layer thusformed on the substrate 3 were performed by means of reflection highenergy electron diffraction and by use of an atomic force microscope(AFM), respectively. The intensity of the electron beam used forexternal excitation was set to 5 kV and 5 nA. The measurement wascarried out at room temperature.

FIG. 12 shows a diffraction pattern obtained by use of reflection highenergy electron diffraction. As is apparent from the result, a clearspot and Kikuchi line showing a single crystal were observed. Theappearance of the Kikuchi line shows that the crystalline structure isextremely excellent.

From the surface image by AFM shown in FIG. 13, the surface shape isextremely flat and provided with the flatness necessary for the lightemitting device.

FIG. 14 shows the emission spectrum in the external excitation byelectron beam irradiation. A near ultraviolet emission peak with highintensity which seems to be a band edge emission was observed in 380 nm.The emission in a visible region by impurities or lattice defect asshown in FIG. 15, which was reported in a ZnO layer by the conventionalMO-CVD method using highly reactive diethyl zinc, was hardly observed.

From the above results, it can be concluded that an external excitationtype luminescence device that is one of light emitting devices can beobtained. Needless to say, a laser light emitting device can be obtainedby forming a reflector on this element to form a resonator.

The preferred embodiment of this invention is described in Example inreference to the drawings. This invention is never limited by such anembodiment, and various changes or additions within the scope neverdeparting from the purport of this invention can be involved in thisinvention.

For example, although a general electric heater is used as thepreheating heater 9 in the above preheating, an electromagnetic wavegenerator such as magnetron or the like may be used as the preheatingmeans to output electromagnetic waves satisfactorily absorbable by awater molecule, particularly, electromagnetic waves of 2.4 GHz band toexecute the heating, since there is the possibility that a crystal ofhigh quality with good reproducibility can be obtained by efficientlyexciting the oxygen atom directly coordinated to the zinc atom,particularly the oxygen atom in the water molecule in the use of thezinc acetylacetonate monohydrate as the zinc-containing organiccompound. Further, it is also included in the preheating that thereactivity is enhanced by directly exciting the oxygen atom in the watermolecule or acetone functional group by laser beam irradiation or thelike.

In the above device, although oxygen is supplied to the reaction chamber1 from the outside, the supply of oxygen may be properly stopped whenthe oxygen in the water molecule or the oxygen in the acetylacetonemolecule can be used as reactive oxygen.

The MO-CVD is carried out at atmospheric pressure in the above. However,this invention is never limited thereby, and the MO-CVD may be carriedout in a proper low pressure. To improve the growth rate, plasma or thelike may be introduced to accelerate the decomposition of thezinc-containing organic compound.

1. A zinc oxide semiconductor material comprising at least zinc andoxygen as constituent elements and having a zinc oxide layer grown on asingle crystal substrate, wherein the crystal orientation plane of thezinc oxide layer is oriented to the a-axis of the wurtzite structure,the zinc oxide layer has an (110) orientation, and the zinc oxidesemiconductor material is formed by chemical vapor deposition (CVD) byuse of an organic metal of βdiketone compound as raw material, whereinthe constituent element of a substrate material is included in the rangeof 0.001–1 at. % near the interface with the substrate material wherethe zinc oxide semiconductor material is formed.
 2. The zinc oxidesemiconductor material of claim 1 wherein the zinc oxide layer is grownon a R-plane substrate.
 3. A zinc oxide semiconductor material accordingto claim 1, wherein the organic metal of β-diketone compound is zincacetylacetonate (Zn(acac)₂; wherein ac represents acetylacetone).
 4. Azinc oxide semiconductor material comprising at least zinc and oxygen asconstituent elements and having a zinc oxide layer grown on a singlecrystal substrate, wherein the crystal orientation plane of the zincoxide layer is oriented to the a-axis of the wurtzite structure, thezinc oxide layer has an (110) orientation, and the zinc oxidesemiconductor material is formed by chemical vapor deposition (CVD) byuse of zinc acetylacetonate or zinc acetylacetonate hydrate as rawmaterial, wherein the constituent element of a substrate material isincluded in the range of 0.001–1 at. % near the interface with thesubstrate material where the zinc oxide semiconductor material isformed.
 5. The zinc oxide semiconductor material of claim 4, wherein thezinc acetylacetonate is selected from the group consisting ofZn(C₅H₇O₂)₂, Zn(CH₃COCHCOCH₃) and (Zn(acac)₂; wherein acac representsacetylacetone).
 6. The zinc oxide semiconductor material of claim 4,wherein the zinc oxide layer is grown on a R-plane substrate.
 7. A lightemitting device containing the zinc oxide semiconductor material ofclaim
 1. 8. A light emitting device containing the zinc oxidesemiconductor material of claim 4.